The invention relates to a conditional access system for controlling the access of receivers of end-users to data content transmitted from a data content source in an uplink system, the uplink system employing a scrambler for scrambling the content supplied from the content source, an entitlement control message generator for generating entitlement control messages containing a control word and an entitlement identification and a transmitter for transmitting the scrambled content and the entitlement control messages, in which access system a descrambler, an entitlement control message decoder and means for recording entitlement identifications are associated to the receiver, and in which access system, if a match between the entitlement identification in the entitlement control message and the recorded entitlement identification exists, the entitlement control message decoder supplies a control word to the descrambler for descrambling a part of the received scrambled content for which the receiver is entitled.
Such a conditional access system is known from the article xe2x80x9cA single conditional access system for satellite-cable and terrestrial TVxe2x80x9d published in IEEE Transactions on Consumer Electronics, Vol. 35, No. 3, August 1989, pages 464-468.
For having access to an offered content item of information or data or television programs the end-user can buy an entitlement Such an entitlement gives the right to access a predefined program or service. The known conditional access systems control access to the content based on bought entitlements.
Such known conditional access systems have the disadvantage that after an entitlement has been bought it is not possible for the end-user to influence this right, other than by requesting the entitlement to be cancelled.
The invention has the object to provide a conditional access system of the abovementioned kind, in which more user influence is allowed.
This object is achieved by the invention in that the content is subdivided into scenes having their own scene identification and the uplink system is provided with a scene identification generator connected to the entitlement control message generator for incorporating the scene identifications in the entitlement control messages and that means are provided for registering the accessed scenes at the receiver.
By the division of the content in scenes the end-user has the possibility to interrupt watching of a (television) program or other service and to continue watching at a more appropriate moment when that same program is broadcasted again. The end-user could be charged for those parts of a service that he has actually accessed.
The invention will be explained further by reference to The enclosed figure showing The architecture of a preferred embodiment of a conditional access system according to X invention.
A service is a sequence of programs under the control of a broadcaster, which can be broadcasted as part of a schedule. The service is the central referenced entity.
According to the invention a further entity is introduced, which is called scene hereafer. Scenes divide content into separate parts.
The scenes may be defined on the basis of time (e.g., each scene lasts 5 minutes) on the basis of the amount of data (e.g, each scene represents 1 MByte of data), or in a content related way (e.g., each scene represents a website in a broadcast data carousel). Each scene is identified by an identification, hereafter called scene number.